The existing technology for the distillation systems dates from 50 to 60 years ago. In spite of that, it is still possible to further improve energy optimization.
The following documents are herein described as prior-art references with regard to distillation processes with energy optimization. However, none of them anticipate the matter of the present invention.
Katzen, R. discloses in his paper titled “A Low Energy Distillation System for the Production of Ethanol Fuel” (“Sistema de Destilacão de Baixo Consumo Energético para a Producão de Etanol Carburante”, Copersucar International Symposium on Sugar and Alcohol, p. 560 , São Paulo, June, 1985) a study about an energy optimization system for the production of anhydrous alcohol fuel, working with columns at different pressures. The top product of the highest pressure column acts as a reboiler of the other columns operating at atmospheric pressure. With this, the system presents a reduction in the consumption of steam.
Leppanen, O. in his paper titled “Energy Consumption in the Distillation of Fuel Alcohol” (Copersucar International Symposium on Sugar and Alcohol, São Paulo, June, 1985) also relates to energy optimization in the process of anhydrous alcohol distillation using columns at different pressures. In this paper, two case studies were made: one of them used a higher pressure at the rectification column (4.5 bar) and atmospheric pressure in the dehydration and evaporation columns. The other system used the dehydration column operating at a reduced pressure (about 0.6 bar). The two results have presented a lower steam consumption when compared to the conventional system. Comparing both of them, it is noted that there is a lower consumption of steam in the system utilizing higher pressure columns. As cited in the abovementioned paper, the use of a distillation column operating at a lower pressure reduces the consumption of steam. With the use of a vacuum column, the pressure delta between the columns could be even higher and the steam consumption could be further reduced. However, this system requires special care, such as, for instance, with the fact that the alcohol-water azeotrope disappears at the pressure of 0.1 bar. In addition, there is a need to minimize the head loss in the column.
U.S. Pat. No. 6,171,449 (Washington Group International) discloses a process for the distillation separation of styrene monomer from ethylbenzene utilizing the split-feed technology. Although it is not specifically directed to the production of alcohol, this patent describes a distillation process wherein a stream is split to feed into two distillation columns, one at high pressure and the other at low pressure, together with a reboiler that uses the thermal energy of the top of one column to supply heat to the other.
Patent application JP 58-183634 (Japanese Industry and Foreign Trade Ministry) discloses a process for producing anhydrous ethanol by the split-feed system wherein the feed is fed in series into at least two distillation columns operating at low pressure. The product is taken from the last column in the form of vapor and is fed into an adsorption column, which adsorbs moisture in order to obtain anhydrous ethanol. At the same time, part or all of the reflux liquid at the last column is fed with the fraction of the distillation columns except the final one.
Patent application PI 8203199 (Codistil SA Dedini) discloses a system for producing alcohol employing a split-feed distillation process, wherein the liquid load is split into two columns: a distillation column for the water and alcohol mixture and a rectification column for the distilled product, both being fed in parallel with the water and alcohol mixture of the process. The energy used is high-pressure steam, injected in the first column, and the top vapors emitted by it are used for heating the second column. In both columns, the heating process is obtained using a vertical thermosiphon reboiler.
Patent application PI 0302605-1 (Dedini S/A Indústrias de Base) discloses a process for producing anhydrous alcohol from a main stream of sugar cane wine to be fed to the steps of distillation and dehydration. This process comprises the steps of: a) removing a secondary stream of wine from a primary stream of wine; b) distilling the secondary stream of wine separately from the primary stream, so as to produce a condensed phlegma; c) recycling the stream of condensed phlegma to the primary stream of wine; d) simultaneously distilling said streams of condensed phlegma with the primary stream of wine, in order to produce a stream of hydrated alcohol and e) dehydrating the stream of hydrated alcohol in a dehydration column by means of the condensation heat of a stream of phlegma vapor from the distillation of the secondary stream of wine.